Much as the International Cricket Council would like us to think that it is important, there are few people who truly believe the one-day international world rankings matter in a form of the game in which there is a championship every four years to decide unequivocally who is best.

At the moment that side are India but in three years' time, when the World Cup takes place in Australia and New Zealand, both England and South Africa, each of whom have come close to winning it without lighting the cigar, dream that steady improvement will give them a first success. ODI cricket therefore is about the short term but only to a degree: the more extensive agenda underpinning that is a four-year cycle in which to establish the bulk of the team and give them sufficient matches at the top level to make sure they can be labelled as experienced.

England are in transition and playing well enough – both with Kevin Pietersen before this summer and without him – with 10 wins and no defeats against Pakistan, West Indies and Australia, who were beaten 4-0, since the tour of India at the back end of last year. They are also unbeaten in a home series since 2009.

Pietersen's sudden decision to retire from international one-day cricket came at a time when he had been given the opportunity to open the batting with the captain, Alastair Cook, and had responded with a brace of centuries in the Emirates, his first in 37 innings going back to 2008. England's response was to promote Ian Bell in his place and he delivered with a hundred, only his second in 114 matches, and three half centuries. Added responsibility also seemed to allow Ravi Bopara to flourish in the middle order and he has contributed four half centuries since his promotion to No4, with his bowling an additional and important element to England's recent success.

Bopara has been missing from England cricket since withdrawing from the side before the Headingley Test for personal reasons. "It's been a tough time for him," said Cook in Cardiff, where the series starts on Friday, "but he loves playing cricket. I've seen him in training, having a bit of fun with a big smile on his face. He played such an important part against Australia batting at four, his bowling was exceptional as well. He has been such a key part of our one-day side over the past year."

South Africa are regenerating too and will go into the series knowing that the last time they were in England, they were not able to recapture the intensity of the Test series, which they won, losing all four of the completed ODIs that followed.

England have won eight and lost one of the past 12 matches between the two countries (with three washouts), their only defeat coming in Cape Town at the end of 2009. Among the victories was a win in Chennai at the last World Cup, the last time the sides met and a match in which Bopara top-scored for England and Stuart Broad produced figures of four for 15.

Broad is missing from this series, undergoing rest together with strength and conditioning training. But with a new ball from each end, there is a chance now for Jimmy Anderson to re-establish himself as an incisive leader of the attack and for Steve Finn to continue the progress that made him such a force on the slow pitches of India.

South Africa, though, have also had a successful 2012 in ODIs, winning six and losing two, both at home to Sri Lanka. It is to his bowlers, particularly Dale Steyn and Morne Morkel, that the one-day captain, AB de Villiers, will be looking to attack what they perceive to be an order light in competitive batting, with Craig Kieswetter at six and Tim Bresnan likely to go in at seven.

"I think they are a little bit light in the batting department," De Villiers said. "They've got Bresnan that I think they rely on quite a bit coming in at seven. The reason why they're playing conservatively up front is because they're a batter light. They don't go with the wicketkeeper at seven like most teams do. But I don't think they've got a set blueprint.

"They can play around with options and they've got a wonderful ODI side. Their ODI team are a totally different unit and I can't see them carrying a lot of scars from the Test series. There is just a tiny little mental factor but if we don't start well [in Cardiff] we lose that momentum right away."

England have no fitness worries and Jade Dernbach or Chris Woakes will replace Broad from the team who beat Australia at Old Trafford. South Africa have a concern over Albie Morkel, who injured an ankle during their warm-up match against Gloucestershire.